Allergy tests are done to determine if substances are causing an allergic reaction. A negative test result means there were no skin changes in response to the allergen and most often means that you are not allergic to the substance. A person may rarely have a negative allergy test and still be allergic to the substance.
A positive result means you reacted to a substance. A positive result often means the symptoms you are having are due to exposure to that substance. A stronger response generally means you are more sensitive to the substance. People can have a positive response to a substance with allergy skin testing, but not have any problem with that substance in everyday life.
The skin prick test tests for immediate hypersensitivity to environmental and food allergies. Small amounts of substances that may be causing your symptoms are placed on the skin, most often on the forearm, upper arm, or back. The skin is then pricked so the allergen goes under the skin's surface. The health care provider closely watches the skin for swelling and redness or other signs of a reaction. Results are usually seen within 20-25 minutes.
Patch testing is a method used to diagnose the cause of skin rashes that may occur if a person is allergic to commonly found chemicals which the skin routinely comes in contact with. Possible allergens are taped to the skin for 48 hours in order to test for delayed-type hypersensitivity. The health care provider will look at the area in 72-96 hours.
Skin tests are usually accurate. Your healthcare provider will consider your symptoms and the results of your skin test to suggest lifestyle changes that you can make to avoid substances that may be causing your symptoms.